NAME

       makeparallel - command line tool for communication with the GNU make jobserver

SYNOPSIS

       To run a multi-thread or multi-process binary inside GNU make using makeparallel, add:

                  +makeparallel subprocess arguments

       to a rule.  For example, to wrap ninja in make, use something like:

                  +makeparallel ninja -f build.ninja

       To determine the size of the jobserver pool, add:

                  +makeparallel echo > make.jobs

       to  a rule that is guarantee to run alone (i.e. all other rules are either dependencies of
       the makeparallel rule, or the depend on the  makeparallel  rule.   The  output  file  will
       contain  the  -j<num> flag passed to the parent make process, or -j1 if no flag was found.
       Since GNU make will run makeparallel during the execution phase, after all variables  have
       been  set  and evaluated, it is not possible to get the output of makeparallel into a make
       variable.  Instead, use a shell substitution to read the output file directly in a recipe.
       For example:

                  echo Make was started with $$(cat make.jobs)

DESCRIPTION

       makeparallel    communicates    with    the    GNU    make   jobserver   (http://make.mad-
       scientist.net/papers/jobserver-implementation/) in order claim  all  available  jobs,  and
       then passes the number of jobs claimed to a subprocess with -j<jobs>.

       The  number  of  available jobs is determined by reading tokens from the jobserver until a
       read would block.  If the makeparallel rule is the only one running  the  number  of  jobs
       will  be the total size of the jobserver pool, i.e. the value passed to make with -j.  Any
       jobs running in parallel with with the makeparellel rule will reduce the  measured  value,
       and thus reduce the parallelism available to the subprocess.

AUTHORS

       The Android Open Source Project.

                                                                                  MAKEPARALLEL(1)